Biocompatible hydrophilic compositions

ABSTRACT

Durable hydrophilic compositions comprising aliphatic polyester, an anionic surfactant, and in some embodiments, a carrier.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/061,088, filed Jun. 12, 2008, which is incorporatedherein by reference.

BACKGROUND

Thermoplastic polymers are widely employed to create a variety ofproducts, including blown and cast films, extruded sheets, foams, fibersand products made therefrom, woven and knitted fabrics, and non-wovenfibrous webs. Traditionally, many of these articles have been made frompetroleum-based thermoplastics such as polyolefins.

There is a growing interest in replacing these petroleum based polymerswith resource renewable polymers, i.e. polymers derived from plant basedmaterials. Ideal resource renewable polymers are “carbon dioxideneutral” meaning that as much carbon dioxide is consumed in growing theplant based material as is given off when the product is made anddisposed of Biodegradable materials have adequate properties to permitthem to break down when exposed to conditions which lead to composting.Examples of materials thought to be biodegradable include aliphaticpolyesters such as poly(lactic acid), poly(glycolic acid),poly(caprolactone), copolymers of lactide and glycolide, poly(ethylenesuccinate), poly(butylene succinate), polyhydroxybutyrate, andcombinations thereof.

Degradation of aliphatic polyesters can occur through multiplemechanisms including hydrolysis, transesterification, chain scission,and the like. Instability of such polymers during processing can occurat elevated temperatures as described in WO 94/07941 (Gruber et al.).

The processing of aliphatic polyesters as microfibers has been describedin U.S. Pat. Nos. 6,645,618. 6,111,160 (Gruber et al.) discloses the useof melt stable polylactides to form nonwoven articles via melt blown andspunbound processes.

Many thermoplastic polymers used in these products, such aspolyhydroxyalkanoates (PHA), are inherently hydrophobic. That is, as awoven, knit, or nonwoven such as a spunbond fabric, they will not absorbwater. There are a number of uses for thermoplastic polymers where theirhydrophobic nature either limits their use or requires some effort tomodify the surface of the shaped articles made therefrom. For example,polylactic acid has been reported to be used in the manufacture ofnonwoven webs that are employed in the construction of absorbentarticles such as diapers, feminine care products, and personalincontinence products (U.S. Pat. No. 5,910,368). These materials wererendered hydrophilic through the use of a post treatment topicalapplication of a silicone copolyol surfactant. Such surfactants are notthermally stable and can break down in an extruder to yieldformaldehyde.

U.S. Pat. No. 7,623,339 discloses a polyolefin resin renderedantimicrobial and hydrophilic using a combination of fatty acidmonoglycerides and enhancer(s).

Coating methods to provide a hydrophilic surface are known, but alsohave some limitations. First of all, the extra step required in coatingpreparation is expensive and time consuming. Many of the solvents usedfor coating are flammable liquids or have exposure limits that requirespecial production facilities. The quantity of surfactant can also belimited by the solubility of the surfactant in the coating solvent andthe thickness of the coating.

Post treatment of the thermoplastic polymer can be undesirable for atleast two other reasons. First, it can be more expensive since itrequires additional processing steps of surfactant application anddrying. Second, PHAs are polyesters, and thus prone to hydrolysis. It isdesirable to limit the exposure of PHA polymers to water which can bepresent in the surfactant application solution. Furthermore, thesubsequent drying step at elevated temperature in the wet web is highlyundesirable.

DISCLOSURE OF INVENTION

The present disclosure is directed to a composition, article and methodfor making a durable hydrophilic and preferably biocompatiblecomposition. The inventive compositions may be melt-processable and haveutility in a variety of food safety, medical and water purificationapplications.

Exemplary aliphatic thermoplastic polyesters are poly(lactic acid),poly(glycolic acid), poly(lactic-co-glycolic acid), polyhydroxybutyrate,polyhydroxyvalerate, blends, and copolymers thereof. Blends may be madeusing a variety of other polymers including aromatic polyesters,aliphatic/aromatic copolyesters such as those described in U.S. Pat. No.7,241,838 which is incorporated herein by reference, cellulose esters,cellulose ethers, thermoplastic starches, ethylene vinyl acetate,polyvinyl alcohol, ethylenevinyl alcohol, and the like. In blendedcompositions which include thermoplastic polymers which are notaliphatic polyesters, the aliphatic polyester is typically present at aconcentration of greater than 60% by weight of total thermoplasticpolymer, preferably greater than 70% by weight of total thermoplasticpolymer and most preferably greater than about 75% by weight ofthermoplastic polymer.

Inventive articles comprise molded polymeric articles, polymeric sheets,polymeric fibers, woven webs, nonwoven webs, porous membranes, polymericfoams, as well as layered compositions such as thermal or adhesivelaminates, and combinations thereof made of the compositions describedabove. Examples of useful articles of this disclosure are wound contactmaterials made of a film, foam and/or woven or nonwoven comprising theinventive composition and surgical drapes or surgical gowns, as well aspersonal hygiene articles such as diapers, feminine hygiene pads and thelike made of the inventive composition.

The method of the present disclosure comprises providing the aliphaticthermoplastic polyester and the surfactants as described herein, andmixing these materials sufficiently to yield a biocompatible, durablehydrophilic composition.

In one aspect, the polymer composition is melt processable, such thatthe polymer is capable of being extruded.

In another aspect, the polymer is solvent soluble or dispersible and thecomposition may be solvent cast, solvent spun to form films or fibers,or foams.

The melt processable composition of aliphatic polyesters and surfactantsexhibit durable hydrophilicity. In some cases the surfactant may bedissolved in or along with a surfactant carrier. The surfactant carrierand/or surfactant may be a plasticizer for the thermoplastic aliphaticpolyester. The plasticized aliphatic polyester generally has a lowermelt processing temperature and can yield a more flexible outputmaterial.

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere in thespecification.

The term “biodegradable” means degradable by the action of naturallyoccurring microorganisms such as bacteria, fungi and algae and/ornatural environmental factors such as hydrolysis, transesterification,exposure to ultraviolet or visible light (photodegradable) and enzymaticmechanisms or combinations thereof.

The term “biocompatible” means biologically compatible by not producingtoxic, injurious or immunological response in living tissue.Biocompatible materials may also be broken down by biochemical and/orhydrolytic processes and absorbed by living tissue. Test methods usedinclude ASTM F719 for applications where the compositions contact tissuesuch as skin, wounds, mucosal tissue including in an orifice such as theesophagus or urethra, and ASTM F763 for applications where thecompositions are implanted in tissue.

The term “durable hydrophilic” means that the composition, typically infiber or fabric form, remains water absorbent when aged at least 30 daysat 23° C. and preferably at least 40 days at 23° C.

The recitation of numerical ranges by endpoints includes all numberssubsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3,3.8, 4, and 5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. Thus, for example, reference to acomposition containing “a compound” includes a mixture of two or morecompounds. As used in this specification and the appended claims, theterm “or” is generally employed in its sense including “and/or” unlessthe content clearly dictates otherwise.

Unless otherwise indicated, all numbers expressing quantities oringredients, measurement of properties and so forth used in thespecification and claims are to be understood as being modified in allinstances by the term “about.” Accordingly, unless indicated to thecontrary, the numerical parameters set forth in the foregoingspecification and attached claims are approximations that can varydepending upon the desired properties sought to be obtained by thoseskilled in the art utilizing the teachings of the present invention. Atthe very least, and not as an attempt to limit the application of thedoctrine of equivalents to the scope of the claims, each numericalparameter should at least be construed in light of the number ofreported significant digits and by applying ordinary roundingtechniques.

DETAILED DESCRIPTION

The present invention discloses the use of melt additive anionicsurfactants, optionally combined with surfactant carriers such aspolyethylene glycol, to impart stable durable hydrophilicity toaliphatic polyester thermoplastics such as polyhydroxyalkanoates (e.g.polylactic acid). This invention is particularly useful for makinghydrophilic absorbent polylactic acid nonwoven/film laminate drapes usedin surgery as well as personal care absorbents such as feminine hygienepads, diapers, incontinence pads, and the like.

Hydrophilicity, or the lack thereof, can be measured in a variety ofways. For example, when water contacts a porous nonwoven web that ishydrophobic or has lost its hydrophilicity, the water does not flow, orflows undesirably slowly, through the web. Importantly the fibers andwebs of the present invention exhibit stable hydrophilicity (waterabsorbency). That is, they remain hydrophilic after aging in a clean butporous enclosure such as a poly/Tyvek pouch for over 30 days at 23° C.or lower and preferably for over 40 days.

Preferred materials of this invention wet with water and thus have anapparent surface energy of great than 72 dynes/cm (surface tension ofpure water). The most preferred materials of this invention instantlyabsorb water and remain water absorbent after aging for 10 days at 5°C., 23° C. and 45° C. More preferred materials of this inventioninstantly absorb water and remain water absorbent after aging for 20days at 5° C., 23° C. and 45° C. Even more materials of this inventioninstantly absorb water and remain water absorbent after aging for 30days at 5° C., 23° C. and 45° C.

Most preferred compositions remain hydrophilic (water absorbent) aftermore than 10 days at 45° C., preferably more than 30 days and mostpreferably greater than 40 days, when tested according to the methodsdescribed in the Examples. The preferred fabrics are instantaneouslywettable and absorbent and are capable of absorbing water at very highinitial rates.

In one aspect, this invention provides a durable hydrophilic,thermoplastic composition comprising at least one thermoplasticaliphatic polyester polymer, e.g., polylactic acid, polyhydroxybutyrateand the like, and one or more surfactants selected from the group ofalkyl, alkaryl, alkenyl or aralkyl sulfate; alkyl, alkaryl, alkenyl oraralkyl sulfonate; alkyl, alkaryl, alkenyl or aralkyl carboxylate; oralkyl, alkaryl, alkenyl or aralkyl phosphate surfactants. Thecompositions may optionally comprise a surfactant carrier which may aidprocessing and/or enhance the hydrophilic properties. The blend of thesurfactant(s) and optionally a surfactant carrier is present in the meltextruded fiber in an amount sufficient to impart durable hydrophilicityto the fiber at its surface.

Preferably the surfactant is soluble in the carrier at extrusiontemperatures at the concentrations used. Solubility can be evaluated,for example, as the surfactant and carrier form a visually transparentsolution in a 1 cm path length glass vial when heated to extrusiontemperature (e.g. 150-190° C.). Preferably the surfactant is soluble inthe carrier at 150° C. More preferably the surfactant is soluble in thecarrier at less than 100° C. so that it can be more easily incorporatedinto the polymer melt. More preferably the surfactant is soluble in thecarrier at 25° C. so that no heating is necessary when pumping thesolution into the polymer melt.

Preferably the surfactant is soluble in the carrier at greater than 10%by weight, more preferably greater than 20% by weight, and mostpreferably greater than 30% by weight in order to allow addition of thesurfactant without too much carrier present, which may plasticize thethermoplastic. Typically the surfactants are present at present in atotal amount of at least 0.25 wt-%, preferably at least 0.50 wt-%, morepreferably at least 0.75 wt-%, based on the total weight of thecomposition. In certain embodiments, in which a very hydrophilic web isdesired, or a web that can withstand multiple assaults with aqueousfluid, the surfactant component comprises greater than 2 wt. %, greaterthan 3 wt. %, or even greater than 5 wt. % of the degradable aliphaticpolyester polymer composition. In certain embodiments, the surfactantstypically are present at 0.25 wt. % to 8 wt. % of the degradablealiphatic polyester polymer composition.

The surfactant and optional carrier should be relatively free ofmoisture in order to facilitate extrusion and to prevent hydrolysis ofthe aliphatic polyester. Preferably the surfactant and optional carrier,either alone or in combination, comprise less than 5% water, morepreferably less than 2% water, even more preferably less than 1% water,and most preferably less than 0.5% water by weight as determined by aKarl-Fisher titration.

In another aspect, the present invention provides durable hydrophilicfilms and durable hydrophilic fabrics and webs constructed from saidfibers. The invention also provides useful articles made from durablehydrophilic fabrics and webs including medical drapes, wound dressings,medical gowns, aprons, filter media, industrial wipes and personal careand home care products such as diapers, facial tissue, facial wipes, wetwipes, dry wipes, disposable absorbent articles and garments such asinfant diapers or training pants, adult incontinence products, femininehygiene products such as sanitary napkins and panty liners and the like.The invention also provides useful antifog films when using transparentaliphatic polyesters. These antifog films may be used in food packaging,for safety eyewear and the like.

In yet another aspect, this invention provides multi-layer, aqueousliquid-absorbent articles comprising an aqueous media impervious backingsheet. For example, importantly some surgical drapes are liquidimpervious to prevent liquid that is absorbed into the top sheet fromwicking through to the skin surface where it would be contaminated withbacteria present on the skin. In other embodiments the construction mayfurther comprise an aqueous media permeable topsheet, and an aqueousliquid-absorbent (i.e., hydrophilic) layer constructed of theabove-described web or fabric juxtaposed there between, useful inconstructing for example, disposable diapers, wipes or towels, sanitarynapkins, and incontinence pads.

The compositions of this invention are “relatively homogenous”. That is,the compositions can be produced by melt extrusion with good mixing andat the time of extrusion would be relatively homogenous in concentrationthroughout. It is recognized, however, that over time and/or with heattreatment the surfactant(s) may migrate to become higher or lower inconcentration at certain points, such as at the surface of the fiber.

In another aspect, a method of preparing durable hydrophilic fibers froma mixture or blend of thermoplastic film-forming aliphatic polyester,and at least one surfactant, is provided. The melt of the blend isprocessed or shaped, for example, by extrusion or molding to producefibers with the surfactants dissolved or dispersed within the fiber andpresent at the surfaces of the fiber to render those surfaces durablyhydrophilic. Because some surfactants demonstrate thermal sensitivity,the processing temperatures in the extruder are preferably kept belowabout 300° C., more preferably below about 250° C., and even morepreferably below 200° C. where those surfactants are exposed to suchtemperatures given the particular processing technique. The durablehydrophilicity is achieved without requiring post fiber finishingoperations, e.g. application of additional surfactant, because the fiberis durably hydrophilic as extruded, however, heating the web afterextrusion may help to bloom surfactant to the surface and improvehydrophilicity. This is done at temperatures at or above the glasstransition temperature of the thermoplastic(s) and is typically lessthan 120° C. and even less than 100° C.

The hydrophilicity imparted to the fiber compositions described hereinis done using at least one melt additive surfactant. Suitable anionicsurfactants include alkyl, alkenyl, alkaryl, or arakyl sulfate, alkyl,alkenyl, alkaryl, or arakyl sulfonate, alkyl, alkenyl alkaryl, or arakylphosphate, alkyl, alkenyl, alkaryl, or arakyl carboxylate or acombination thereof. The alkyl and alkenyl groups may be linear orbranched. These surfactants may be modified as is known in the art. Forexample, as used herein an “alkyl carboxylate” is a surfactant having analkyl group and a carboxylate group but it may also include, forexample, bridging moieties such as polyalkylene oxide groups, e.g.,isodeceth-7 carboxylate sodium salt is an alkyl carboxylate having abranched chain of ten carbons (C10) alkyl group, seven moles of ethyleneoxide and terminated in a carboxylate.

The surfactants of this invention can be conveniently compounded withthe resin in a concentrate (masterbatch) composition, which can thenmixed be with the virgin thermoplastic polymer in the hopper orelsewhere along the extruder as long as blending is achieved to render asubstantially uniform mixture. Alternatively, the surfactant may beadded as into the extruder directly (without precompounding), forexample, using a positive displacement pump or weight loss feeder. Thisis most conveniently done if the surfactant is dissolved or dispersed ina surfactant carrier such as a polyalkylene oxide or polyol.

Certain classes of hydrocarbon, silicone, and fluorochemical surfactantshave each been described as useful for imparting hydrophilicity topolyolefins. These surfactants typically are contacted with thethermoplastic resin in one of two ways: (1) by topical application,e.g., spraying or padding or foaming, of the surfactants from aqueoussolution to the extruded nonwoven web or fiber followed by drying, or(2) by incorporation of the surfactant into the polyolefin melt prior toextrusion of the web. The latter is much preferable but is difficult tofind a surfactant that will spontaneously bloom to the surface of thefiber or film in sufficient amount to render the article hydrophilic. Aspreviously described, webs made hydrophilic by topical application of asurfactant suffer many drawbacks. Some are reported to also havediminished hydrophilicity after a single contact with aqueous media.Additional disadvantages to topical application of a surfactant toimpart hydrophilicity may include skin irritation from the surfactantitself, non-uniform surface and bulk hydrophilicity, and the additivecost resulting from the necessity of an added processing step in thesurfactant application. Incorporating one or more surfactants into tothe thermoplastic polymer as a melt additive alleviates the problemsassociated with topical application and in addition may provide a softer“hand” to the fabric or nonwoven web into which it is incorporated. Thechallenge as previously stated, is finding a surfactant that willreliably bloom to the surface of the article in sufficient amount toimpart hydrophilicity and then to remain properly oriented at thesurface to ensure durable hydrophilicity.

The fibers described herein remain hydrophilic and water absorbent afterrepeated insult with water, e.g. saturating with water, wringing out andallowing to dry. Preferred compositions of this invention include arelatively homogenous composition comprising at least one aliphaticpolyester resin (preferably polylactic acid), at least one alkylsulfate,alkylene sulfate, or aralkyl or alkaryl sulfate, carboxylate, orphosphate surfactant, typically in an amount of at 0.25 wt % to 8 wt %,and optionally a nonvolatile carrier in a concentration of 1 wt % to 8wt %, as described in more detail below.

Preferred porous fabric constructions of the present invention producedas knits, wovens, and nonwovens have apparent surface energies greaterthan 60 dynes/cm, and preferably greater than 70 dynes/cm when tested bythe Apparent Surface Energy Test disclosed in the Examples. Preferredporous fabric materials of this invention wet with water and thus havean apparent surface energy of greater than 72 dynes/cm (surface tensionof pure water). The most preferred materials of this invention instantlyabsorb water and remain water absorbent after aging for 10 days at 5°C., 23° C. and 45° C. “Instant” absorption means a 25 μl drop of waterthat is gently placed on the fabric does not form a discrete droplet onthe surface of the fabric but is absorbed into the pores.

Preferred film constructions of the present invention are wettable byaqueous fluids and have a contact angle with deionized water of lessthan 40 degrees, preferably less than 30 degrees, and most preferablyless than 20 degrees when measured using a Tantec Contact Angle Meter(Shaumburg, Ill.), described as the half-angle technique in U.S. Pat.No. 5,268,733.

The present invention also discloses a method of making a relativelyhomogenous hydrophilic aliphatic polyester composition comprising ananionic surfactant and optionally a surfactant carrier by blending thesein a melt process, and forming a film, fiber, or foam.

The present invention also discloses a method of making a relativelyhomogenous hydrophilic aliphatic polyester composition comprising ananionic surfactant and optionally a surfactant carrier by blending theseto form a concentrate, blending the concentrate with additionalaliphatic polyester in a melt process, and forming a film, fiber, orfoam.

The present invention also discloses a method of making a relativelyhomogenous hydrophilic aliphatic polyester composition comprising ananionic surfactant and optionally a surfactant carrier by blending thesein a melt process, forming a film, fiber, or foam, and post heating thefilm, fiber or foam to a temperature greater than 50° C.

The present invention also discloses a method of making a relativelyhomogenous hydrophilic aliphatic polyester composition comprising ananionic surfactant and optionally a surfactant carrier by blending theseto form a concentrate, blending the concentrate with additionalaliphatic polyester in a melt process, forming a film, fiber, or foamand post heating the film, fiber, or foam to a temperature greater than50° C.

Polyesters

Aliphatic polyesters useful in the present invention include homo- andcopolymers of poly(hydroxyalkanoates), and homo- and copolymers of thosealiphatic polyesters derived from the reaction product of one or morepolyols with one or more polycarboxylic acids that are typically formedfrom the reaction product of one or more alkanediols with one or morealkanedicarboxylic acids (or acyl derivatives). Polyesters may furtherbe derived from multifunctional polyols, e.g. glycerin, sorbitol,pentaerythritol, and combinations thereof, to form branched, star, andgraft homo- and copolymers. Polyhydroxyalkanoates generally are formedfrom hydroxyacid monomeric units or derivatives thereof. These include,for example, polylactic acid, polyhydroxybutyrate, polyhydroxyvalerate,polycaprolactone and the like. Miscible and immiscible blends ofaliphatic polyesters with one or more additional semicrystalline oramorphous polymers may also be used.

One useful class of aliphatic polyesters are poly(hydroxyalkanoates),derived by condensation or ring-opening polymerization of hydroxy acids,or derivatives thereof. Suitable poly(hydroxyalkanoates) may berepresented by the formula:H(O—R—C(O)—)_(n)OHwhere R is an alkylene moiety that may be linear or branched having 1 to20 carbon atoms, preferably 1 to 12 carbon atoms optionally substitutedby catenary (bonded to carbon atoms in a carbon chain) oxygen atoms; nis a number such that the ester is polymeric, and is preferably a numbersuch that the molecular weight of the aliphatic polyester is at least10,000, preferably at least 30,000, and most preferably at least 50,000daltons. Although higher molecular weight polymers generally yield filmsand fibers with better mechanical properties, for both melt processedand solvent cast polymers, excessive viscosity is typically undesirable.It is a significant advantage of the present invention that thesurfactant carrier and/or surfactant component in many embodimentsplasticizes the polyester component allowing for melt processing andsolvent casting of higher molecular weight polymers. Thus, the molecularweight of the aliphatic polyester is typically less than 1,000,000,preferably less than 500,000, and most preferably less than 300,000daltons. R may further comprise one or more caternary (i.e. in chain)ether oxygen atoms. Generally, the R group of the hydroxy acid is suchthat the pendant hydroxyl group is a primary or secondary hydroxylgroup.

Useful poly(hydroxyalkanoates) include, for example, homo- andcopolymers of poly(3-hydroxybutyrate), poly(4-hydroxybutyrate),poly(3-hydroxyvalerate), poly(lactic acid) (as known as polylactide),poly(3-hydroxypropanoate), poly(4-hydropentanoate),poly(3-hydroxypentanoate), poly(3-hydroxyhexanoate),poly(3-hydroxyheptanoate), poly(3-hydroxyoctanoate), polydioxanone,polycaprolactone, and polyglycolic acid (i.e. polyglycolide). Copolymersof two or more of the above hydroxy acids may also be used, for example,poly(3-hydroxybutyrate-co-3-hydroxyvalerate),poly(lactate-co-3-hydroxypropanoate), poly(glycolide-co-p-dioxanone),and poly(lactic acid-co-glycolic acid). Blends of two or more of thepoly(hydroxyalkanoates) may also be used, as well as blends with one ormore semicrystalline or amorphous polymers and/or copolymers.

The aliphatic polyester may be a block copolymer of poly(lacticacid-co-glycolic acid). Aliphatic polyesters useful in the inventivecompositions may include homopolymers, random copolymers, blockcopolymers, star-branched random copolymers, star-branched blockcopolymers, dendritic copolymers, hyperbranched copolymers, graftcopolymers, and combinations thereof.

Another useful class of aliphatic polyesters includes those aliphaticpolyesters derived from the reaction product of one or more alkanediolswith one or more alkanedicarboxylic acids (or acyl derivatives). Suchpolyesters have the general formula:

where R′ and R″ each represent an alkylene moiety that may be linear orbranched having from 1 to 20 carbon atoms, preferably 1 to 12 carbonatoms, and m is a number such that the ester is polymeric, and ispreferably a number such that the molecular weight of the aliphaticpolyester is at least 10,000, preferably at least 30,000, and mostpreferably at least 50,000 daltons, but less than 1,000,000, preferablyless than 500,000 and most preferably less than 300,000 daltons. Each nis independently 0 or 1. R′ and R″ may further comprise one or morecaternary (i.e. in chain) ether oxygen atoms.

Examples of aliphatic polyesters include those homo- and copolymersderived from (a) one or more of the following diacids (or derivativethereof): succinic acid; adipic acid; 1,12 dicarboxydodecane; fumaricacid; glutartic acid; diglycolic acid; and maleic acid; and (b) one ofmore of the following diols: ethylene glycol; polyethylene glycol;1,2-propane diol; 1,3-propanediol; 1,2-propanediol; 1,2-butanediol;1,3-butanediol; 1,4-butanediol; 2,3-butanediol; 1,6-hexanediol; 1,2alkane diols having 5 to 12 carbon atoms; diethylene glycol;polyethylene glycols having a molecular weight of 300 to 10,000 daltons,and preferably 400 to 8,000 daltons; propylene glycols having amolecular weight of 300 to 4000 daltons; block or random copolymersderived from ethylene oxide, propylene oxide, or butylene oxide;dipropylene glycol; and polypropylene glycol, and (c) optionally a smallamount, i.e., 0.5-7.0 mole percent of a polyol with a functionalitygreater than two, such as glycerol, neopentyl glycol, andpentaerythritol.

Such polymers may include polybutylene succinate homopolymer,polybutylene adipate homopolymer, polybutyleneadipate-succinatecopolymer, polyethylenesuccinate-adipate copolymer, polyethylene glycolsuccinate homopolymer and polyethylene adipate homopolymer.

Commercially available aliphatic polyesters include poly(lactide),poly(glycolide), poly(lactide-co-glycolide),poly(L-lactide-co-trimethylene carbonate), poly(dioxanone),poly(butylene succinate), and poly(butylene adipate).

Useful aliphatic polyesters include those derived from semicrystallinepolylactic acid. Poly(lactic acid) or polylactide has lactic acid as itsprinciple degradation product, which is commonly found in nature, isnon-toxic and is widely used in the food, pharmaceutical and medicalindustries. The polymer may be prepared by ring-opening polymerizationof the lactic acid dimer, lactide. Lactic acid is optically active andthe dimer appears in four different forms: L,L-lactide, D,D-lactide,D,L-lactide (meso lactide) and a racemic mixture of L,L- and D,D-. Bypolymerizing these lactides as pure compounds or as blends,poly(lactide) polymers may be obtained having differentstereochemistries and different physical properties, includingcrystallinity. The L,L- or D,D-lactide yields semicrystallinepoly(lactide), while the poly(lactide) derived from the D,L-lactide isamorphous.

The polylactide preferably has a high enantiomeric ratio to maximize theintrinsic crystallinity of the polymer. The degree of crystallinity of apoly(lactic acid) is based on the regularity of the polymer backbone andthe ability to crystallize with other polymer chains. If relativelysmall amounts of one enantiomer (such as D-) is copolymerized with theopposite enantiomer (such as L-) the polymer chain becomes irregularlyshaped, and becomes less crystalline. For these reasons, whencrystallinity is favored, it is desirable to have a poly(lactic acid)that is at least 85% of one isomer, at least 90% of one isomer, or atleast 95% of one isomer in order to maximize the crystallinity.

An approximately equimolar blend of D-polylactide and L-polylactide isalso useful. This blend forms a unique crystal structure having a highermelting point (˜210° C.) than does either the D-poly(lactide) andL-(polylactide) alone (˜190° C.), and has improved thermal stability.See H. Tsuji et al., Polymer, 40 (1999) 6699-6708.

Copolymers, including block and random copolymers, of poly(lactic acid)with other aliphatic polyesters may also be used. Useful co-monomersinclude glycolide, beta-propiolactone, tetramethylglycolide,beta-butyrolactone, gamma-butyrolactone, pivalolactone, 2-hydroxybutyricacid, alpha-hydroxyisobutyric acid, alpha-hydroxyvaleric acid,alpha-hydroxyisovaleric acid, alpha-hydroxycaproic acid,alpha-hydroxyethylbutyric acid, alpha-hydroxyisocaproic acid,alpha-hydroxy-beta-methylvaleric acid, alpha-hydroxyoctanoic acid,alpha-hydroxydecanoic acid, alpha-hydroxymyristic acid, andalpha-hydroxystearic acid.

Blends of poly(lactic acid) and one or more other aliphatic polyesters,or one or more other polymers may also be used. Examples of usefulblends include poly(lactic acid) and poly(vinyl alcohol), polyethyleneglycol/polysuccinate, polyethylene oxide, polycaprolactone andpolyglycolide.

Poly(lactide)s may be prepared as described in U.S. Pat. Nos. 6,111,060(Gruber, et al.), 5,997,568 (Liu), 4,744,365 (Kaplan et al.), 5,475,063(Kaplan et al.), 6,143,863 (Gruber et al.), 6,093,792 (Gross et al.),6,075,118 (Wang et al.), 5,952,433 (Wang et al.), WO 98/24951 (Tsai etal.), WO 00/12606 (Tsai et al.), WO 84/04311 (Lin), U.S. Pat. Nos.6,117,928 (Hiltunen et al.), 5,883,199 (McCarthy et al.), WO 99/50345(Kolstad et al.), WO 99/06456 (Wang et al.), WO 94/07949 (Gruber etal.), WO 96/22330 (Randall et al.), and WO 98/50611 (Ryan et al.), thedisclosure of each incorporated herein by reference. Reference may alsobe made to J. W. Leenslag, et al., J. Appl. Polymer Science, vol. 29(1984), pp 2829-2842, and H. R. Kricheldorf, Chemosphere, vol. 43,(2001) 49-54.

The molecular weight of the polymer should be chosen so that the polymermay be processed as a melt or cast from a solvent. For polylactide, forexample, the molecular weight may be from about 10,000 to 1,000,000daltons, and is preferably from about 30,000 to 300,000 daltons. By“melt-processable”, it is meant that the aliphatic polyesters are fluidor can be pumped or extruded at the temperatures used to process thearticles (e.g. films), and do not degrade or gel at those temperaturesto the extent that the physical properties are so poor as to be unusablefor the intended application. Thus, many of the materials describedherein may be made into films by extrusion, casting, thermal pressing,and the like. They can be made into nonwovens using melt processes suchas spunbond, blown microfiber, melt spinning and the like. Certainembodiments also may be injection molded. Generally, weight averagemolecular weight (M_(W)) of the polymers is above the entanglementmolecular weight, as determined by a log-log plot of viscosity versusnumber average molecular weight (M_(n)). Above the entanglementmolecular weight, the slope of the plot is about 3.4, whereas the slopeof lower molecular weight polymers is 1.

The aliphatic polyester component of the composition typically comprisesat least 60 weight percent, preferably at least 70 weight percent, andmost preferably at least 75 weight percent, based on the total weight ofthe durable hydrophilic composition.

Surfactants

Compositions of the present invention include one or more surfactants tohelp wet the surface and/or to aid in contacting and killingmicroorganisms. As used herein the term “surfactant” means an amphiphile(a molecule possessing both polar and nonpolar regions which arecovalently bound) capable of reducing the surface tension of waterand/or the interfacial tension between water and an immiscible liquid.The term is meant to include soaps, detergents, emulsifiers, surfaceactive agents, and the like.

In applications in which biodegradability is important, it may bedesirable to incorporate biodegradable surfactants, which typicallyinclude ester and/or amide groups that may be hydrolytically orenzymatically cleaved. In certain preferred embodiments, the surfactantsuseful in the compositions of the present invention are anionicsurfactants selected from the group consisting of alkyl, alkenyl,alkaryl and arakyl sulfonates, sulfates, phosphonates, phosphates andmixtures thereof. Included in these classes are alkylalkoxylatedcarboxylates, alkyl alkoxylated sulfates, alkylalkoxylated sulfonates,and alkyl alkoxylated phosphates, and mixtures thereof. The preferredalkoxylate is made using ethylene oxide and/or propylene oxide with0-100 moles of ethylene and propylene oxide per mole of hydrophobe. Incertain more preferred embodiments, the surfactants useful in thecompositions of the present invention are selected from the groupconsisting of sulfonates, sulfates, phosphates, carboxylates andmixtures thereof. In one aspect, the surfactant is selected from(C8-C22) alkyl sulfate salts (e.g., sodium salt); di(C8-C13alkyl)sulfosuccinate salts; C8-C22 alkyl sarconsinate; C8-C22 alkyllactylates; and combinations thereof. Combinations of varioussurfactants can also be used.

The anionic surfactants useful in this invention are described in moredetail below and include surfactants with the following structure:R—(O)_(x)SO₃ ⁻M⁺ and R—CO₂ ⁻M⁺Where:

-   R=alkyl or alkylene of C8-C30, which is branched or straight chain,    or C12-C30 aralkyl, and may be optionally substituted with 0-100    alkylene oxide groups such as ethylene oxide, propylene oxide    groups, oligameric lactic and/or glycolic acid or a combination    thereof.-   X=0 or 1-   M=alkali metal salts, preferably Li+, K+, or Na+, or amine salts    including tertiary and quaternary amines.

Examples include C8-C18 alkane sulfonates; C8-C18 secondary alkanesulfonates; alkylbenzene sulfonates such as dodecylbenzene sulfonate;C8-C18 alkyl sulfates; alkylether sulfates such as sodium trideceth-4sulfate, sodium laureth 4 sulfate, sodium laureth 8 sulfate (such asthose available from Stepan Company, Northfield Ill.), docusate sodiumalso known as dioctylsulfosuccinate, sodium salt; lauroyl lacylate andstearoyl lactylate (such as those available from RITA Corporation,Crystal Lake, Il under the PATIONIC tradename), and the like.

Surfactants with the following structure can also be useful:(R—O)₂P(O)O⁻M⁺ or R—OP(O)(O⁻)₂M⁺ ₂Where R and M are defined above. Examples include stearyl phosphate(available as Sippostat 0018 from Specialty Industrial Products, Inc.,Spartanburg, S.C.); Cetheth-10 PPG-5 phosphate (Crodaphos SG, availablefrom Croda USA, Edison N.J.); laureth-4 phosphate; and dilaureth-4phosphate.

Exemplary anionic surfactants include, but are not limited to,sarcosinates, glutamates, alkyl sulfates, sodium or potassium alkylethsulfates, ammonium alkyleth sulfates, ammonium laureth-n-sulfates,laureth-n-sulfates, isethionates, glycerylether sulfonates,sulfosuccinates, alkylglyceryl ether sulfonates, alkyl phosphates,aralkyl phosphates, alkylphosphonates, and aralkylphosphonates. Theseanionic surfactants may have a metal or organic ammonium counterion.Certain useful anionic surfactants are selected from the groupconsisting of: sulfonates and sulfates such as alkyl sulfates,alkylether sulfates, alkyl sulfonates, alkylether sulfonates,alkylbenzene sulfonates, alkylbenzene ether sulfates,alkylsulfoacetates, secondary alkane sulfonates, secondaryalkylsulfates, and the like. Many of these can be represented by theformulas:R²⁶—(OCH₂CH₂)_(n6)(OCH(CH₃)CH₂)_(p2)-(Ph)_(a)-(OCH₂CH₂)_(m3)—(O)_(b)—SO₃⁻M⁺andR²⁶—CH[SO₃-M⁺]-R²⁷wherein:

a and b=0 or 1; n6, p2, and m3=0-100 (preferably 0-20); R²⁶ is definedas below provided at least one R²⁶ or R²⁷ is at least C8; R²⁷ is a(C1-C12)alkyl group (saturated straight, branched, or cyclic group) thatmay be optionally substituted by N, O, or S atoms or hydroxyl, carboxyl,amide, or amine groups; Ph=phenyl; and M is a cationic counterion suchas H, Na, K, Li, ammonium, or a protonated tertiary amine such astriethanolamine or a quaternary ammonium group.

In the formula above, the ethylene oxide groups (i.e., the “n6” and “m3”groups) and propylene oxide groups (i.e., the “p2” groups) can occur inreverse order as well as in a random, sequential, or block arrangement.R²⁶ may be an alkylamide group such as R²⁸—C(O)N(CH₃)CH₂CH₂— as well asester groups such as —OC(O)—CH₂— wherein R²⁸ is a (C8-C22)alkyl group(branched, straight, or cyclic group). Examples include, but are notlimited to: alkyl ether sulfonates, including lauryl ether sulfates(such as POLYSTEP B12 (n=3-4, M=sodium) and B22 (n=12, M=ammonium)available from Stepan Company, Northfield, Ill.) and sodium methyltaurate (available under the trade designation NIKKOL CMT30, NikkoChemicals Co., Tokyo, Japan); secondary alkane sulfonates, includingsodium (C14-C17)secondary alkane sulfonates (alpha-olefin sulfonates)(such as Hostapur SAS available from Clariant Corp., Charlotte, N.C.);methyl-2-sulfoalkyl esters such as sodium methyl-2-sulfo(C12-16)esterand disodium 2-sulfo(C12-C16)fatty acid (available from Stepan Company,Northfield, Ill. under the trade designation ALPHASTEP PC-48);alkylsulfoacetates and alkylsulfosuccinates available as sodiumlaurylsulfoacetate (under the trade designation LANTHANOL LAL, StepanCompany, Northfield, Ill.) and disodiumlaurethsulfosuccinate (STEPANMILDSL3, Stepan Company, Northfield, Ill.); alkylsulfates such asammoniumlauryl sulfate (available under the trade designation STEPANOLAM from Stepan Company, Northfield, Ill.); dialkylsulfosuccinates suchas dioctylsodiumsulfosuccinate (available as Aerosol OT from CytecIndustries, Woodland Park, N.J.).

Suitable anionic surfactants also include phosphates such as alkylphosphates, alkylether phosphates, aralkylphosphates, and aralkyletherphosphates. Many may be represented by the formula:[R²⁶—(Ph)_(a)-O(CH₂CH₂O)_(n6)(CH₂CH(CH₃)O)_(p2)]_(q2)—P(O)[O⁻M⁺]_(r),wherein:

Ph, R²⁶, a, n6, p2, and M are defined above; r is 0-2; and q2=1-3; withthe proviso that when q2=1, r=2, and when q2=2, r=1, and when q2=3, r=0.As above, the ethylene oxide groups (i.e., the “n6” groups) andpropylene oxide groups (i.e., the “p2” groups) can occur in reverseorder as well as in a random, sequential, or block arrangement. Examplesinclude a mixture of mono-, di- andtri-(alkyltetraglycolether)-o-phosphoric acid esters generally referredto as trilaureth-4-phosphate (available under the trade designationHOSTAPHAT 340KL from Clariant Corp.); as well as PPG-5 ceteth 10phosphate (available under the trade designation CRODAPHOS SG from CrodaInc., Parsipanny, N.J.), and mixtures thereof.

One or more surfactants may be used in and/or on the compositionsdescribed herein at a suitable level to produce the desired result. Insome embodiments, when used in the composition, they are present in atotal amount of at least 0.25 wt. %, at least 0.5 wt-%, at least 0.75wt-%, at least 1.0 wt-%, or at least 2.0 wt-%, based on the total weightof the composition. In certain embodiments, in which a very hydrophilicweb is desired, or a web that can withstand multiple assaults withaqueous fluid, the surfactant component comprises greater than 2 wt. %,greater than 3 wt. %, or even greater than 5 wt. % of the degradablealiphatic polyester polymer composition.

In other embodiments, the surfactants are present in a total amount ofno greater than 20 wt. %, no greater than 15 wt. %, no greater than 10wt. %, or no greater than 8 wt. %, based on the total weight of theready to use composition.

Preferred surfactants have a melting point of less than 200° C.,preferably less than 190° C., more preferably less than 180° C., andeven more preferably less than 170° C.

For melt processing, preferred surfactant components have low volatilityand do not decompose appreciably under process conditions. The preferredsurfactants contain less than 10 wt. % water, preferably less than 5%water, and more preferably less than 2 wt. % and even more preferablyless than 1% water (determined by Karl Fischer analysis). Moisturecontent is kept low in order to prevent hydrolysis of the aliphaticpolyester or other hydrolytically sensitive compounds in thecomposition, which will help to give clarity to extruded films orfibers.

We have found that it is particularly convenient to use a surfactantpredissolved in a non-volatile carrier. Importantly, the carrier istypically thermally stable and can resist chemical breakdown atprocessing temperatures which may be as high as 150° C., 180° C., 200°C. or even as high as 250° C. In a preferred embodiment, the surfactantcarrier is a liquid at 23° C. Preferred carriers include polyalkyleneoxides such as polyethylene glycol, polypropylene glycol, random andblock copolymers of ethylene oxide and propylene oxide, thermally stablepolyhydric alcohols such as propylene glycol, glycerin, polyglycerin,and the like. The polyalkylene oxides may be linear or brancheddepending on the initiating polyol. For example, a polyethylene glycolinitiated using ethylene glycol would be linear but one initiated withglycerin, trimethylolpropane, or pentaerythritol would be branched.

Preferred carriers also may include low molecular weight esters ofpolyhydric alcohols such as triacetin, glyceryl caprylate/caprate,acetyltributylcitrate, and the like.

The solubilizing liquid carriers may alternatively be selected fromnon-volatile organic solvents. For purposes of the present invention, anorganic solvent is considered to be nonvolatile if greater than 80% ofthe solvent remains in the composition throughout the mixing and meltprocesses. Because these liquids remain in the melt processablecomposition, they function as plasticizers, generally lowering the glasstransition temperature of the composition.

Since the carrier is substantially nonvolatile it will in large partremain in the composition and may function as an organic plasticizer. Asused herein a plasticizer is a compound having a molecular weight lessthan 1000 daltons which when added to the polymer composition results ina decrease in the glass transition temperature. Possible surfactantcarriers include compounds containing one or more hydroxyl groups, andparticularly glycols such glycerin; 1,2 pentanediol; 2,4 diethyl-1,5pentanediol; 2-methyl-1,3-propanediol; as well as monofunctionalcompounds such 3-methoxy-methylbutanol (“MMB”). Additional examples ofnonvolatile organic plasticizers include polyethers, includingpolyethoxylated phenols such as Pycal 94 (phenoxypolyethyleneglycol);alkyl, aryl, and aralkyl ether glycols (such as those sold under theDowanol™ tradename by Dow Chemical Company, Midland Mich.) including butnot limited to propyelene glycolmonobutyl ether (Dowanol PnB),tripropyleneglycol monobutyl ether (Dowanol TPnB), dipropyeleneglycolmonobutyl ether (Dowanol DPnB), propylene glycol monophenyl ether(Dowanol PPH), and propylene glycol monomethyl ether (Dowanol PM);polyethoxylated alkyl phenols such as Triton X35 and Triton X102(available from Dow Chemical Company, Midland Mich.); mono orpolysubstituted polyethylene glycols such as PEG 400 diethylhexanoate(TegMer 809, available from CP Hall Company), PEG 400 monolaurate(CHP-30N available from CP Hall Company) and PEG 400 monooleate (CPH-41Navailable from CP Hall Company); amides including higher alkylsubstituted N-alkyl pyrrolidones such as N-octylpyrrolidone;sulfonamides such as N-butylbenzene sulfonamide (available from CP HallCompany); triglycerides; citrate esters; esters of tartaric acid;benzoate esters (such as those available from Velsicol Chemical Corp.,Rosemont Ill. under the Benzoflex tradename) including dipropyleneglycoldibenzoate (Benzoflex 50) and diethylene glycol dibenzoate;benzoic acid diester of 2,2,4 trimethyl 1,3 pentane diol (Benzoflex354), ethylene glycol dibenzoate, tetraetheylene glycoldibenzoate, andthe like; polyethylene glycols and ethylene oxide propylene oxide randomand block copolymers having a molecular weight less than 10,000 daltons,preferably less than about 5000 daltons, more preferably less than about2500 daltons; and combinations of the foregoing. As used herein the termpolyethylene glycols refer to glycols having 26 alcohol groups that havebeen reacted with ethylene oxide or a 2 haloethanol.

Preferred polyethylene glycols are formed from ethylene glycol,propylene glycol, glycerin, trimethylolpropane, pentaerithritol, sucroseand the like. Most preferred polyethylene glycols are formed fromethylene glycol, propylene glycol, glycerin, and trimethylolpropane.Polyalkylene glycols such as polypropylene glycol, polytetramethyleneglycol, or random or block copolymers of C2 C4 alkylene oxide groups mayalso be selected as the carrier. Polyethylene glycols and derivativesthereof are presently preferred. It is important that the carriers becompatible with the polymer. For example, it is presently preferred touse non-volatile non-polymerizable plasticizers that have less than 2nucleophilic groups, such as hydroxyl groups, when blended with polymershaving acid functionality, since compounds having more than twonucleophilic groups may result in crosslinking of the composition in theextruder at the high extrusion temperatures. Importantly, thenon-volatile carriers preferably form a relatively homogeneous solutionwith the aliphatic polyester polymer composition in the extruder, andremain a relatively homogeneous composition upon cooling, such that theextruded composition is relatively uniform in surfactant concentration.

Optional Components

Other optional components may be included in the compositions describedherein.

An antimicrobial component may be added to impart antimicrobial activityto the compositions. The antimicrobial component is that component ofthe composition that provides at least part of the antimicrobialactivity, i.e., it has at least some antimicrobial activity for at leastone microorganism. It is preferably present in a large enough quantityto be leached from the composition and kill bacteria. It may also bebiodegradable and/or made or derived from renewable resources such asplants or plant products. Biodegradable antimicrobial components caninclude at least one functional linkage such as an ester or amidelinkage that can be hydrolytically or enzymatically degraded.

Examples of antimicrobial components suitable for use in the presentinvention include those described in Applicants' co-pending application,U.S. Patent Application Publication No. 2008-0142023A1, incorporated byreference herein in its entirety.

Certain antimicrobial components are uncharged and have an alkyl oralkenyl hydrocarbon chain containing at least 7 carbon atoms. For meltprocessing, preferred antimicrobial components have low volatility anddo not decompose under process conditions. The preferred antimicrobialcomponents contain less than 2 wt. % water, and more preferably lessthan 0.10 wt. % (determined by Karl Fischer analysis). Moisture contentis kept low in order to prevent hydrolysis of the aliphatic polyesterand to give clarity to extruded film. The moisture level should besimilarly controlled for solvent cast films that are dried at elevatedtemperatures, e.g. greater than 50° C.-60° C.

When used, the antimicrobial component content (as it is ready to use)is typically at least 1 wt. %, 2 wt. %, 5 wt. %, 10 wt. % and sometimesgreater than 15 wt. %. In certain embodiments, for example inapplications in which a low strength is desired, the antimicrobialcomponent comprises greater than 20 wt. %, greater than 25 wt. %, oreven greater than 30 wt. % of the composition.

Certain antimicrobial components are amphiphiles and may be surfaceactive. For example, certain antimicrobial alkyl monoglycerides aresurface active. For certain embodiments of the invention that includeantimicrobial components, the antimicrobial component is considereddistinct from a surfactant component.

The compositions may further comprise organic and inorganic fillers. Forimplantable applications biodegradable, resorbable, or bioerodibleinorganic fillers may be particularly appealing. These materials mayhelp to control the degradation rate of the polymer composition. Forexample, many calcium salts and phosphate salts may be suitable.Exemplary biocompatible resorbable fillers include calcium carbonate,calcium sulfate, calcium phosphate, calcium sodium phosphates, calciumpotassium phosphates, tetracalcium phosphate, alpha-tricalciumphosphate, beta-tricalcium phosphate, calcium phosphate apatite,octacalcium phosphate, dicalcium phosphate, calcium carbonate, calciumoxide, calcium hydroxide, calcium sulfate dihydrate, calcium sulfatehemihydrate, calcium fluoride, calcium citrate, magnesium oxide, andmagnesium hydroxide. A particularly suitable filler is tribasic calciumphosphate (hydroxy apatite).

Plasticizers may be used with the aliphatic polyester thermoplastic andinclude, for example, glycols such glycerin; propylene glycol,polyethoxylated phenols, mono or polysubstituted polyethylene glycols,higher alkyl substituted N-alkyl pyrrolidones, sulfonamides,triglycerides, citrate esters, esters of tartaric acid, benzoate esters,polyethylene glycols and ethylene oxide propylene oxide random and blockcopolymers having a molecular weight less than 10,000 daltons preferablyless than about 5000 daltons, more preferably less than about 2500daltons; and combinations thereof. As discussed above, the surfactantcarrier can also function as a plasticizer, and may be distinct from aplasticizer added as an optional component.

Other additional components include antioxidant, colorant such as dyesand/or pigments, antistatic agents, fluorescent brightening agents, odorcontrol agents, perfumes and fragrances, active ingredients to promotewound healing or other dermatological activity, combinations thereof andthe like.

Applications and Methods of Manufacturing

Articles comprising the inventive composition may be made by processesknown in the art for making products such as polymer sheets from polymerresins. For many applications, such articles can be placed in water at23° C. without substantial loss of physical integrity (e.g. tensilestrength) after being immersed 2 hours and dried. Typically, thesearticles contain little or no water. The water content in the articleafter extruding, injection molding or solvent casting is typically lessthan 10% by weight, preferably less than 5% by weight, more preferablyless than 1% by weight and most preferably less than 0.2% by weight.Polymeric sheets may be formed by an extrusion process from the resincompositions described herein, resulting in hydrophilic polymer sheetsuseful in applications such as medical drapes and garments, personalcare items and food wrapping.

Articles that may be made of the compositions may include medical drapesand gowns, including surgical drapes, procedural drapes, plasticspecialty drapes, incise drapes, barrier drapes, barrier gowns, SMSgowns, and the like; wound dressings, wound absorbents, and woundcontact layers; surgical sponges use to absorb blood and body fluidsduring surgery; surgical implants; as well as tubular extrusion productssuch as vascular catheters, urinary catheters, endotracheal tubes,shunts, wound drains and other medical devices.

Importantly the preferred hydrophilic additive surfactants of thecompositions described herein allow for adhesive, thermal, and/orultrasonic bonding of fabrics and films made thereof. Articles may besolvent, heat, or ultrasonically welded together as well as being weldedto other compatible articles. The compositions may be used inconjunction with other materials to form constructions such assheath/core materials, laminates, compound structures of two or morematerials, or useful as coatings on various medical devices.

The compositions described herein are particularly suitable for use insurgical drapes and gowns due to their unique wetting properties. Forexample, the polylactic acid/surfactant compositions have durablehydrophilicity as described herein. Non-woven web and sheets comprisingthe inventive compositions have good tensile strength; can be heatsealed to form strong bonds allowing specialty drape fabrication; can bemade from renewable resources which can be important in disposableproducts; and can have high surface energy to allow wettability andfluid absorbency in the case of non-wovens (as measured for nonwovensusing the Apparent Surface Energy test and absorbing water); and forfilms the contact angles often are less than 50 degrees, preferably lessthan 30 degrees, and most preferably less than 20 degrees when thecontact angles are measured using distilled water on a flat film usingthe half angle technique described in U.S. Pat. No. 5,268,733 and aTantec Contact Angle Meter, Model CAM-micro, Schamberg, Ill. In order todetermine the contact angle of materials other than films, a film of theexact same composition should be made by solvent casting.

It is believed that such non-woven, film and tube materials can besterilized by gamma radiation or electron beam without significant lossof physical strength. A measure of physical strength can be tensilestrength for a 1 mil thick film that does not decrease by more than 20%,and preferably by not more than 10%, after exposure to 2.5 Mrad gammaradiation from a cobalt gamma radiation source and aged at 23-25° C. for7 days.

The hydrophilic characteristic of the inventive composition may improvearticles such as wound and surgical dressings by improving absorbency.If the composition is used in a wound dressing backing film, the filmmay be partially (e.g. zone or pattern) coated or completely coated withvarious adhesives, including but not limited to pressure sensitiveadhesives (PSAs), such as acrylic and block copolymer adhesives,hydrogel adhesives, hydrocolloid adhesives, and foamed adhesives.

PSAs can have a relatively high moisture vapor transmission rate toallow for moisture evaporation. Suitable pressure sensitive adhesivesinclude those based on acrylates, polyurethanes, KRATON and other blockcopolymers, silicones, rubber based adhesives as well as combinations ofthese adhesives. The preferred PSAs are medical adhesives that areapplied to skin such as the acrylate copolymers described in U.S. Pat.No. RE 24,906, the disclosure of which is hereby incorporated byreference, particularly a 97:3 iso-octyl acrylate:acrylamide copolymer.Also preferred is an 70:15:15 isooctyl acrylate-ethyleneoxide acrylate:acrylic acid terpolymer, as described in U.S. Pat. No. 4,737,410(Example 31), the disclosure of which is hereby incorporated byreference. Other useful adhesives are described in U.S. Pat. Nos.3,389,827; 4,112,213; 4,310,509; and 4,323,557; the disclosures of whichare hereby incorporated by reference. Inclusion of medicaments orantimicrobial agents in the adhesive is also contemplated, as describedin U.S. Pat. Nos. 4,310,509 and 4,323,557.

Other medical devices that may be made, in whole or in part, of theinventive composition include: sutures, suture fasteners, surgical mesh,slings, orthopedic pins (including bone filling augmentation material),adhesion barriers, stents, guided tissue repair/regeneration devices,articular cartilage repair devices, nerve guides, tendon repair devices,atrial septal defect repair devices, pericardial patches, bulking andfilling agents, vein valves, bone marrow scaffolds, meniscusregeneration devices, ligament and tendon grafts, ocular cell implants,spinal fusion cages, skin substitutes, dural substitutes, bone graftsubstitutes, bone dowels, and hemostats.

The compositions of the present invention may also be useful in consumerhygiene products, such as adult incontinence, infant diapers, femininehygiene products, and others as described in Applicants' co-pendingapplication, U.S. Patent Application Publication No. 2008-0200890A1, andincorporated by reference herein in its entirety.

In one process for making the inventive composition, the aliphaticpolyester in a melt form is mixed in a sufficient amount relative to thesurfactant to yield a polymer composition having hydrophiliccharacteristics as described herein.

A variety of equipment and techniques are known in the art for meltprocessing polymeric compositions. Such equipment and techniques aredisclosed, for example, in U.S. Pat. No. 3,565,985 (Schrenk et al.);U.S. Pat. No. 5,427,842 (Bland et. al.); U.S. Pat. Nos. 5,589,122 and5,599,602 (Leonard); and U.S. Pat. No. 5,660,922 (Henidge et al.).Examples of melt processing equipment include, but are not limited to,extruders (single and twin screw), Banbury mixers, and Brabenderextruders for melt processing the inventive composition.

The ingredients of the composition may be mixed in and conveyed throughan extruder to yield a polymer composition, preferably without polymerdegradation or side reactions in the melt. Potential degradationreactions include transesterification, hydrolysis, chain scission andradical chain decomposition, and process conditions should minimize suchreactions. The processing temperature is sufficient to mix the aliphaticpolyester and surfactant, and allow extruding the composition as a film.Films made with the compositions described herein have properties thatare desirable in applications such as food wrap, e.g., transparent (nothazy) and being free of oily residue on the surface (which mightindicate phase separation of components from the polymer matrix).

The compositions may be solvent cast into a film. The ingredients of thecomposition are typically dissolved or at least partially solvated, andthoroughly mixed in a suitable solvent which is then cast on a surfaceand allowed to evaporate, leaving solids comprising the hydrophilicdurable resin composition.

The invention will be further clarified by the following examples whichare exemplary and not intended to limit the scope of the invention.

Test Methods

Apparent Surface Energy

The method for measuring the surface energy is AATCC Test Method118-1983, with the modifications described below. Surface energiesmeasured according to this modified test method are hereinafter referredto as “apparent” surface energies. AATCC test method 118-1983 determinesthe surface energy of a fabric by evaluating the fabric's resistance towetting by a series of selected hydrocarbon compositions. Thehydrocarbons set forth in AATCC 118-1983, however, only provide formeasurements of surface energy from about 19.8 to 27.3 dynes percentimeter at 25° C. This range is extended by employing variousmixtures of methanol and water in the fabric resistance test. Thecompositions and their representative surface tensions are as follows:

Volume % Surface Tension Liquid No. Methanol/Water (Dynes/cm at 20 C. 765/45 30 8 53/47 35 9 40/60 40 10 25/75 45 11 21/79 50 12 15/85 55 13 8.5/91.5 60

The test procedure is as follows. A specimen of the covering material isplaced flat on a smooth, horizontal surface. Using the method of AATCC118-1983 except that beginning with the lowest number test liquid, 5drops of the liquid are placed on the surface of the fabric on the sidewhich will face the resin impregnated sheet in various locations. Ifthree of the five drops wick into the fabric within 60 seconds, theliquid of the next higher surface energy is used. When at least 3 dropsremain on the fabric surface the apparent surface tension is recorded asthe range of the last two liquids.

EXAMPLES Glossary of Terms

PLA 6202D Polylactic acid (Natureworks, Minnetonka, MN) PLA 4032Polylactic acid (Natureworks, Minnetonka, MN) PLA 4060D Polylactic acid(Natureworks, Minnetonka, MN) Brij 700 Steareth-100 (Sigma Aldrich,Milwaukee, WI) Pationic Sodium lauroyl lactylate (RITA Corporation, 138CCrystal Lake, IL) Carbowax polyethylene glycol (PEG) 400 (Dow Chemical,400 Midland, MI) PEG/DOSS 50% docusate sodium USP in PEG 400, (CytecIndustries, West Patterson, NJ) Hostapon Sodium cocoyl isethionate, 85%,(Clariant, STCI-85 Wayne NJ) Hostapur Sodium C14-C17 alkyl sec.sulfonate, (Clariant, SAS-93G Wayne NJ) Montanov Arachidyl Alcohol (and)Behenyl Alcohol (and) 202 Arachidyl Glucoside (Seppic, Fairfield, NJ)Citroflex acetyl tributyl citrate (Morflex Inc., A4 Greensboro, N.C.)Crodaphos PPG-5 ceteth 10 phosphate (Croda, Inc., SG Parsipanny, NJ)

Examples C1-C3, 1, and 2

The compositions listed in Table 1 were extruded on an experimentalspunbond making line. The spunbond nonwovens were generally made usingthe equipment and processing techniques for spunbond nonwovens describedin U.S. Pat. No. 6,916,752.

Non-woven spunbond PLA samples were made with different concentrationsof surfactants. A non-woven spunbond PLA sample without any surfactantwas also made. This was done for the purpose of evaluating and comparingthe different samples' wettability, aging stability, and generalmechanical properties.

The initial step was to pre-compound the wetting agents into higherconcentration masterbatches. This was done using a 25 mm Berstorff UTXtwin screw extruder, fitted with a standard pelletizing die. The strandswere run through a 12 foot water bath and into a pelletizing puller.

Four masterbatches were made: 1) 95% PLA 6202D and 5% PEG 400

-   -   2) 95% PLA 6202D and 5% PEG/DOSS    -   3) 90% PLA 6202D and 10% Brij 700    -   4) 90% PLA 6202D and 10% Pationic 138C        The PLA was fed using a K-tron Feeder. The other additives were        all fed using a grid melter and were fed into Zone 4. Feed rates        were as follows

PLA Pationic 6202D PEG400 PEGDOSS Brij 700 138C Feed Rate Feed Rate FeedRate Feed Rate Feed Rate Batch (lbs/hr) (lbs/hr) (lbs/hr) (lbs/hr)(lbs/hr) 1 95 5 2 95 5 3 58.5 6.5 4 61.2 6.8The zone temperatures were as follows:

Screw Melt Speed Extrud. Extrud. Zone Die Temp- Batch (RPM) Amp KW Zone1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Zone 7 Zone 8 Zone 9 10 ° F. ° F. 1550 31.9 7 101.2 380 380 380 380 380 380 380 380 380 380 413 2 550 25.35.5 100.5 380 380 380 380 380 380 380 380 380 380 398.73 3 400 23.1 3.798.5 380 380 380 380 380 380 380 380 380 380 403.15 4 400 18.2 2.9 98.5380 380 380 380 380 380 380 380 380 380 387.43After the strands passed through the water bath and the pelletizer, theywere collected in 5 gallon pail liners, with holes in the bottom toallow any excess water to run off. The liners were placed in 5 gallonpails and were raised from the bottom about 4 inches. Once the sampleshad been “drip dried”, the batches were distributed into multiple pansand allowed to crystallize in a batch oven at 65° C. for 12 to 24 hours.

The masterbatches and the virgin PLA were dried for a minimum of 6 hoursin a recirculated drier at 60° C. A web was made with 60 g/sq/m. Melttemperatures were about 190-210° C. When running Masterbatch 4 withPationic 138C, a dramatic viscosity reduction occurred, so thetemperature had to be dropped 160° C. The webs were passed through athrough air bonder on a screen support at a temperature of 90-100° C. inorder lightly bond the web.

Spunbond nonwoven examples were prepared using the masterbatchesdescribed above blended with neat 6202D PLA. All the materials weredried prior to use. The spunbond nonwovens were obtained using aDavis-Standard BLUE RIBBON (DS-20) extruder (Davis Standard Corporation,Pawcatuck, Conn.) using a 2.0 inch/50 mm single screw extruder to feedinto through a pump to an extrusion head including multiple dieorifices.

The die head had a total of 512 orifice holes with an aliphaticpolyester polymer melt throughput of 0.50 g/hole/min (33.83 Ib/hr). Thedie had a transverse length of 7.875 inches (200 mm). The hole diameterwas 0.040 inch (0.889 mm) and L/D ratio of 6. The melt extrusiontemperature at the die of the neat PLA was set at 215° C., while themelt extrusion temperature of PLA with the surfactant additives wasdependent on the type and amount of additives. The temperature wasadjusted in order to make similar webs to the control (pure aliphaticpolyester, PLA). A representative description of the web forming andbonding process is exemplified by U.S. Patent Publication No. US2008/0038976 A1, and incorporated herein as reference in its entirety.

TABLE 1 Aged at 5 C. Aged at 45 C. Time (Days): 0 7 14 28 42 0 7 14 2842 Wet-Out Wet-Out Wet-Out Wet-Out Wet-Out Wet-Out Wet-Out Wet-OutWet-Out Wet-Out Surface Surface Surface Surface Surface Surface SurfaceSurface Surface Surface Tension Tension Tension Tension Tension TensionTension Tension Tension Tension (dynes/ (dynes/ (dynes/ (dynes/ (dynes/(dynes/ (dynes/ (dynes/ (dynes/ (dynes/ Sample Composition cm) cm) cm)cm) cm) cm) cm) cm) cm) cm) C1 95% PLA 6202D; 5% 36 36 36 36 36 36 N/AN/A N/A N/A PEG-400 C2 100% PLA 6202D 36 36 36 36 36 36 36 36 36 36 C395% PLA 6202D; 5% 36 36 36 36 36 36 42 45 45 45 Brij 700 1 95% PLA6202D; 5% 72 72 72 72 72 72 72 72 72 72 DOSS/PEG 2 95% PLA 6202D; 5% 7272 72 72 72 72 72 72 72 72 Pationic 138C

The results indicate that virgin PLA (Comparative Example 2) ishydrophobic with an apparent surface energy of 36dyne/cm throughout theaging at room temperature (23-25° C.) and ambient humidity. Addition ofPEG 400 (MP<23° C.) or the surfactant Brij 700 (MP=51-54° C.) did notimprove the hydrophilicity (Comparative Examples 1 and 3 respectively).Addition of the anionic surfactants docusate sodium (DOSS, MP=153-157°C.) and lauroyl lactylate (Pationic 138C, MP=50-55° C.) (Examples 1 and2) resulted in a dramatic improvement in the hydrophilicity which wasstable over time. The DOSS used was dissolved in a PEG 400 carrier (50%PEG400/50% DOSS solution, MP<23° C.) and formed a transparent solutionwhich simplified processing and may have contributed to the superiorhydrophilicity.

Examples C4-C5 and 3-5

Samples were prepared with PLA 4032 using a Brabender Hot Melt MixerModel No. DR-2051. The Brabender was set to 200° C. and allowed to cometo temperature. The paddle speed was set to 0.70. PLA 4032 waspreweighed on a balance and added to the Brabender. Total mass offinished mixture was 60 g. PLA 4032 was mixed in the Brabender until auniform, molten mixture was made while the specified mass of additivesgradually added. Mixing times were typically 10-20 min. The Braebenderchamber was purged using Unipurge purge resin (Dow Chemical, Midland,Mich.), after every run.

The molten mixtures were pulled from the Brabender and pressed intouniform sheets using a hydraulic press. Samples were pressed at 195° C.and with 20,000 lbs of pressure for 60 seconds between two liners. Theliner was a silicone coated kraft paper release liner. Films were 50-125micron thick.

Formulations of PLA 4032 with various surfactants are shown below inTable 2 along with the contact angle measurements.

TABLE 2 Initial Contact Angle Measurements After 24 hrs at 72 C. Avg.Avg. Example Surfactant % Surf 1 2 3 Angle 1 2 3 Angle Avg. Change C4None 0 60 68 66 64.66667 84 70 78 77.33333 12.66667 C5 Montanov 202 5 8279 86 82.33333 58 66 46 56.66667 −25.66667 3 Pationic 138C 5 10 10 10 1010 10 10 10 0 4 Hostapon STCI 85G 5 58 52 54 54.66667 34 46 30 36.66667−18 5 Hostapur SAS-93G 5 10 10 10 10 30 28 30 29.33333 19.33333The virgin PLA was relatively hydrophobic. Addition of Montanov 202 didnot result in a hydrophilic film. Even after heating the contact anglewas still greater than 50 degrees. The Pationic (alkyl carboxylate)resulted in a very hydrophilic film and heating to 72° C. did not alterthe result. The two sulfonate surfactants behaved differently. Theisethionate surfactant produced a film which was initially relativelyhydrophobic but after heating the contact angle decreased to 37 degrees.The C14-C17 alkyl sulfonate (Hostapur SAS) produced a hydrophilic film,however, aging for 24 hrs at 72° C. increased the contact angle to 29degrees. The inventive compositions resisted fogging when breathed on.

Examples 6-8

The following samples were made and tested according to the proceduredescribed in Examples C4-C5 and Examples 3-5 above.

TABLE 3 Example Number Component 6 7 8 Natureworks PLA 75 70 75 4060DCitroflex A4 20 20 20 Crodafos SG 5 10 2.5 triethanolamine 0 0 2.5 Total100 100 100 Contact angle 30 23 22 Contact angle 28 18 22 Contact angle22 26 20 Average Contact 26.7 22.3 21.3 angle

These results show that the alkoxylated phosphate surfactant, CrodaphosSG, improved the hydrophilicity significantly. In comparison, thecontact angle of PLA with Citroflex plasticizer and no surfactant isstill very hydrophobic, having a contact angle in excess of 60 degrees(data not shown). The addition of Crodaphos SG in the acid form (Example6) reduced the contact angle to less than 27. Addition of more CrodaphosSG (Example 7) reduced the contact angle further and neutralization withtriethanolamine to make the phosphate salt reduced the contact anglefurther yet (Example 8).

While certain representative embodiments and details have been discussedabove for purposes of illustrating the invention, various modificationsmay be made in this invention without departing from its true scope,which is indicated by the following claims.

What is claimed is:
 1. An article comprising a non-woven web of fibers, wherein the fibers comprise a durable hydrophilic composition comprising a blend of: at least one thermoplastic aliphatic polyester, wherein the thermoplastic aliphatic polyester is selected from the group consisting of one or more poly(lactic acid), poly(glycolic acid), poly(lactic-co-glycolic acid), polybutylene succinate, polyhydroxybutyrate, polyhydroxyvalerate, blends, and copolymers thereof; an anionic surfactant incorporated into the polyester, wherein the anionic surfactant is selected from the group consisting of di(C₈-C₁₈) sulfosuccinate salts, C₈-C₂₂ alkyl sarconsinate salts, C₈-C₂₂ alkyl lactylate salts, alkyl alkoxylated phosphates, and alkyl carboxylates; and a surfactant carrier, wherein the surfactant carrier is a liquid at 23° C. and is selected from the group consisting of polyalkylene glycol, polyhydric alcohols, glycerin triglcyerides, citric acid esters, aliphatic diesters and combinations thereof; wherein the composition is free of organic and inorganic fillers, and remains hydrophilic after more than 10 days at 45° C.
 2. The article of claim 1, wherein the anionic surfactant is selected from the group consisting of alkyl carboxylates, alkyl alkoxylated phosphates, and combinations thereof.
 3. The article of claim 1, wherein the anionic surfactant is selected from the group consisting of di(C₈-C₁₈) sulfosuccinate salts, C₈-C₂₂ alkyl lactylate salts and combinations thereof.
 4. The article of claim 1, wherein the anionic surfactant is present in an amount no greater than 8% by weight of the composition, and wherein the anionic surfactant is present in an amount greater than 1% by weight of the composition.
 5. The article of claim 1, wherein the surfactant carrier is present in an amount no greater than 8% by weight of the composition, and wherein the surfactant carrier is present in an amount greater than 1% by weight of the composition.
 6. The article of claim 1, wherein the composition further comprises a plasticizer distinct from the anionic surfactant and distinct from the surfactant carrier.
 7. The article of claim 1, wherein the composition further comprises an antimicrobial component.
 8. The article of claim 1, wherein the nonwoven web is selected from the group consisting of a spunbond web, a blown microfiber web, or a hydroentangled web.
 9. The article of claim 1, wherein the article is a surgical drape or a surgical gown.
 10. The article of claim 1, wherein the article is a wound contact material or a personal hygiene article.
 11. The article of claim 1, wherein the composition further comprises a thermoplastic polymer distinct from the thermoplastic aliphatic polyester; wherein the thermoplastic aliphatic polyester is present in an amount greater than 75% by weight of the total thermoplastic polymer present in the composition.
 12. The article of claim 1, further comprising a layer bonded to the non-woven web of fibers.
 13. The article of claim 12, wherein the layer is thermally bonded to the non-woven web of fibers.
 14. The article of claim 12, wherein the layer is adhesively bonded to the non-woven web of fibers.
 15. The article of claim 12, wherein the layer comprises a polymeric film.
 16. The article of claim 12, wherein the layer comprises a woven or non-woven web.
 17. The article of claim 1, wherein the durable hydrophilic composition comprises a blend of: at least one thermoplastic aliphatic polyester selected from the group consisting of poly(lactic acid), poly(glycolic acid), poly(lactic-co-glycolic acid), and blends thereof; one or more anionic surfactants selected from the group consisting of di(C₈-C₁₈) sulfosuccinate salts, C₈-C₂₂ alkyl lactylate salts, and combinations thereof incorporated into the polyester; and a surfactant carrier selected from the group consisting of polyalkylene glycol, polyhydric alcohols, glycerin triglcyerides, and combinations thereof. 